Method And Device For Aiding The Approach Of An Aircraft During An Approach Phase For The Purpose Of Landing

ABSTRACT

The device ( 1 ) includes means ( 2, 3, 4 ) for determining a limit trajectory representing a flight trajectory which is compatible with the aircraft performance during the approach and which shows the limits for the flight of the aircraft.

The present invention relates to a method and a device for aiding the approach phase of an aircraft, in particular of a transport airplane, upon an approach for a landing on a landing runway of an airport.

More particularly, the present invention aims at determining and at displaying a limit trajectory compatible with the performance of the aircraft when the crew has selected the landing runway. The operational context, for which this invention is particularly adapted, is a common radar guidance by the air traffic control. However, the present invention could also be used for aiding pilots in any situation, wherein the approach phase of the runway does not occur according to a predetermined trajectory.

As known, commercial aircrafts and from now on a lot of aircrafts belonging to the general aviation, are provided with on-board avionics systems allowing to define and memorize a full flight plane as well as to calculate the current position of the aircraft and to guide it according to a programmed trajectory. The latter is generally previously discussed with the authorities in charge of managing the air traffic.

As long as the aircraft follows the programmed trajectory, the avionics system has available all the information needed for managing the evolution of the speed vector of the aircraft, including in this process optimization objectives, possible constraints on the trajectory and the respect of the aircraft performance. On the other hand, when the aircraft deviates from the original flight plane, the on-board systems do not have available all the information needed for predicting and fully manage the evolution of the future trajectory. The latter could be the result of a sequence of instructions from the air traffic control, and most often of a discussion between the pilots and the ground control in the case of a radar guidance, or it could be completely managed by the pilots, for instance upon a sight approach phase. Whatever the situation being considered, humans actors should therefore each time determine, evaluate and implement the trajectory.

The present invention aims at solving these drawbacks and at aiding pilots during the approach phase.

A common radar guidance by the air traffic control is a relatively simple approach method for the pilots. On the other hand, when the external situation becomes complicated, for instance because of bad weather conditions or a very large number of airplanes converging to the runway, it could happen that the interception heading of the approach axis proposed by the air traffic control, or a delayed descent authorization, result in the aircraft following a trajectory that does not allow to dissipate all the energy. There is then a risk of over-speed, or in general of the usual conditions referred to as <<stabilized approach>> not being met.

The same risks could occur when pilots are authorized to carry out a sight approach phase. In such a situation, tiredness, operational pressure, lack of reference points on the ground (for instance upon a night approach phase on the sea) and/or lack of training are all factors able to result in a bad evaluation of the trajectory to be followed.

The present invention aims at solving these drawbacks. It relates to a method for aiding the crew of an aircraft, in particular of a transport airplane, upon an approach phase for the purpose of landing on a landing runway of an airport.

According to this invention, said method is remarkable in that, automatically and repeatedly:

A/ a limit trajectory is built representing a flight trajectory of the aircraft being compatible with the performance of said aircraft upon the approach and which shows the limits where the aircraft can move around, implementing the following operations consisting in:

a) receiving the current speed vector and the current position of the aircraft and position data relative to the landing runway and to a stabilization point;

b) determining as a function of the performance of the aircraft, of its current speed vector and of its current position, a vertical profile which shows the variation of the height and of the speed of the aircraft as a function of a distance and being such that it allows to dissipate the energy of the aircraft upon the approach;

c) determining a horizontal trajectory, allowing the aircraft to reach the stabilization point, respecting the vertical profile determined at step b); and

d) if applicable, determining the position of a limit point on this horizontal trajectory, corresponding to the engagement at the latest of the approach phase according to the limit trajectory; and

B/ the limit trajectory is automatically presented comprising said horizontal trajectory and, if applicable, said limit point, on a viewing screen in the cockpit of the aircraft.

Thus, thanks to the invention, a limit trajectory is determined, and automatically shown, representing a flight trajectory of the aircraft, being compatible with the performance of the latter upon the approach and which shows borders within which the aircraft can move around.

The method according to this invention allows, amongst others, to aid pilots not to exceed the limits defined by the performance of the aircraft, while leaving them free to react on the trajectory for meeting the objectives of passengers comfort, of keeping the visual contact with the runway, and/or of avoiding clouds for instance.

In the case of a usual radar guidance managed by the air traffic control, the interest of such aid is that it is able to provide some support to the pilots with respect to the management of the trajectory and, more particularly, to the negotiation with the ground controllers. Displaying the limit trajectory allows to rapidly evaluate the compatibility between the instructions received from the controllers and the actual performance of the aircraft.

Furthermore, advantageously, at step A/b), a vertical profile is determined linking the current energy state of the aircraft to the energy state required at the stabilization point.

Furthermore, advantageously, said vertical profile is determined according to one of a plurality of different building criteria, one of which is selected by default and the others can be selected by an operator. Preferably, to this end, one of the following building criteria is used:

-   -   one building criterion, wherein the stabilization point is         directly linked to the current altitude;     -   one building criterion, wherein a constant altitude level is         provided at the stabilization point; and     -   one building criterion, wherein a constant altitude level is         provided between the stabilization point and the current point.

Furthermore, advantageously, at step A/, a prediction is carried out for the current speed vector of the aircraft.

Moreover, advantageously, at step A/c), the horizontal trajectory is determined according to one of a plurality of different building rules, one of which is selected by default and the others could be selected by an operator. Preferably, to this end, one of the following building rules is used:

-   -   one building rule, whereby an immediate turn is carried out;     -   one building rule, whereby the current heading is held as long         as possible; and     -   one building rule, whereby the current heading is held until the         approach axis.

Furthermore, advantageously, at step A/, on the horizontal trajectory, the position of an auxiliary limit point is determined, corresponding to a point before which (that is upstream of which) it is not recommended to subject the aircraft to a turn.

The present invention also relates to a method for aiding the crew of an aircraft, in particular of a transport airplane, upon an approach phase for the purpose of landing on a landing runway of an airport.

According to this invention, said device is remarkable in that it comprises:

a processing unit for automatically building a limit trajectory representing a flight trajectory of the aircraft being compatible with the performance of said aircraft upon the approach and which shows limits within which the aircraft can move around, said processing unit comprising:

-   -   means for receiving the current speed vector of the aircraft and         position data, relative to the landing runway and to a         stabilization point;     -   means for determining, as a function of performance of the         aircraft and of its current speed vector, a vertical profile         which shows the variation of the height and of the speed of the         aircraft as a function of a distance and being such that it         allows to dissipate the energy of the aircraft (A) upon the         approach;     -   means for determining a horizontal trajectory allowing the         aircraft to reach the stabilization point, while respecting said         vertical profile; and     -   means for determining, if applicable, the position of a limit         point on this horizontal trajectory, corresponding to the         engagement at the latest of the approach phase according to the         limit trajectory; and

displaying means for automatically show the limit trajectory comprising said horizontal trajectory and if applicable said limit point, on a viewing screen in the cockpit of the aircraft.

The device according to this invention thus determines, taking into consideration the current state of the aircraft, of its performances and of the final objective, a limit trajectory compared to said performance. Displaying this limit trajectory shows the pilot(s) the border of the space where the aircraft can move around, while holding at the same time a piloting modality (either manual or by means of the autopilot) being compatible with the requirements of a short term management and of the role of the human element (on board and on the ground) imposed by the situations being considered.

In a particular embodiment, said device could comprise:

means allowing the pilot to manually activate the display of the limit trajectory on said viewing screen; and/or

means for automatically activating the display of said limit trajectory, for instance as soon as the aircraft deviates from its flight plane upon an approach phase.

The present invention further relates to an aircraft, in particular a transport airplane, being provided with an aiding device such as mentioned hereinabove.

The FIGS. of the appended drawing will better explain how this invention can be implemented. In these FIGS., like reference numerals relate to like components.

FIG. 1 is a block diagram of a device according to the invention.

FIGS. 2, 3A to 3C, 4A to 4C, 5A to 5C and 6A to 6C are diagrams for explaining how to build, according to this invention, a limit trajectory.

The device 1 according to this invention and schematically shown on FIG. 1, aims at aiding the crew of an aircraft A, in particular of a transport airplane, upon an approach phase for the purpose of landing on a landing runway 20 of an airport.

According to this invention, said device 1 comprises:

a set 2 of sources of information;

means 3 allowing an operator to enter data in the device 1;

a processing unit 4 being connected via links 5 and 6 respectively to said set 2 and to said means 3 and being formed so as to automatically build a limit trajectory TL representing a flight trajectory of the aircraft A being compatible with the performance of said aircraft A upon the approach and which shows the limits in which the aircraft A can move around; and

displaying means 7 being connected via a link 8 to the processing unit 4 and being formed so as to automatically present the limit trajectory TL (comprising a horizontal trajectory TH defined in the horizontal plane and set forth below), as well as, if applicable, a limit point to be described hereinafter, on a viewing screen 9 in the cockpit of the aircraft, for instance a navigation screen of the ND (<<Navigation Display>>) type.

Moreover, said processing unit 4 comprises:

means 11 for receiving the current speed vector of the aircraft A and position data, relative to the landing runway 20 and to a stabilization point S, in particular of said set 2 of sources of information;

means 12 for determining, as a function of performance of the aircraft A and of its current speed vector, a vertical profile PV which shows the variation of the height and of the speed of the aircraft A as a function of a distance and being such that it allows to dissipate the energy of the aircraft (A) upon the approach;

means 13 for determining a horizontal trajectory TH allowing the aircraft A to reach the stabilization point S, respecting said vertical profile PV; and

means 14 for determining, if applicable, the position of a limit point on this horizontal trajectory TH, corresponding to the engagement at the latest of the approach phase according to the limit trajectory TL.

Thus, the device 1 according to the invention determines and shows automatically a limit trajectory TL representing a flight trajectory of the aircraft A being compatible with the performance of the latter upon the approach and which shows the limits for the flight of the aircraft A.

Said device 1 allows, amongst other, to aid pilots not to exceed the limits defined by the performance of the aircraft A, while leaving them free to react on the trajectory for meeting the objectives of passengers' comfort, of keeping the visual contact with the runway, and/or of avoiding clouds for instance.

In the case of a usual radar guidance managed by the air traffic control, this aid is advantageous in that it is able to provide some support to pilots with respect to the management of the trajectory and, more particularly, to the negotiation with the ground controllers. Displaying the limit trajectory TL allows to rapidly evaluate the compatibility between the instructions received from the controllers and the actual performance of the aircraft A.

In a particular embodiment, said device 1 further comprises:

means 15 being connected via a link 16, for instance, to the processing unit 4 and allowing the pilot to manually activate the display of the limit trajectory TL on said viewing screen 9; and/or

means 17 being connected via a link 18, for instance also to the processing unit 4 and automatically activating the display of said limit trajectory TL when particular conditions are met, in particular as soon as the aircraft deviates from its flight plane upon an approach phase.

This limit trajectory TL being shown to the pilot indicates the most constraining meeting potential trajectory (that is the shortest one) compared to the performance of the aircraft A. Its display (for instance on a navigation screen) can thus be activated on request of the pilot either via means 15 (for instance a dedicated man/machine interface), or by default, for instance as soon as the aircraft A leaves the reference flight plane upon an approach phase.

The present invention relies on the definition of a target point on the approach axis 22 (as a function of the current need), being entered for instance using means 3, on the knowledge of the current speed vector followed by the aircraft A (or of a short term prediction of said speed vector), received from the means 2, and on the definition of a number of building rules of the trajectory, taking into consideration:

the relative position between the aircraft A and the approach axis 22;

a maximum number of heading changes to be contemplated; and

the definition of the first turn toward the approach axis 22 (immediate turn or delayed turn).

These elements are then transferred to the processing unit 4 generating the optimized trajectory TL, integrating a prediction of the vertical profile PV linking the current energy state of the aircraft A to that required above the threshold 24 of the runway 20.

The means 14 could also determine the position of an auxiliary limit point, to be described below, before which the pilot is not recommended to subject the aircraft A to a turn. The device 1 more specifically allows, via the display of this trajectory, to represent to the pilot constraints of energy type. In the case where the aircraft A is taken on a vector excessively converging to the runway 20, the trajectory produced by the processing unit 4 will allow to dissipate the excess energy. The vision of the resulting trajectory allows the pilot to directly identify the problem associated with the dissipation.

FIG. 2 shows three different cases, corresponding to three different positions of the aircraft A. In each case, the trajectory T1, T2 and T3 between the current position of the aircraft A and a target point Si (in particular said stabilization point S) is the shortest flying trajectory, taking into consideration the necessary distance for dissipating the total energy and the presence of an obstacle OB to be bypassed. The latter influences more specifically the trajectories T2 and T3. On this FIG. 2, the points of limit bend P1, P2 and P3 on the trajectories T1, T2 and T3 are also shown. The trajectories T1, T2 and T3 could be formed, as an illustration, through the method described in patent application FR-10 60191.

As soon as the device 1 is activated, the processing unit 4 recovers with the help of means 2:

the speed vector of the aircraft A; and

the position data relative to the runway 20 and to the stabilization point S.

These elements are received by the means 11 and transmitted to the means 12 usually generating the vertical profile PV (described in terms of distance, height and speed) being required for dissipating the energy, so as to generate the limit profile compared to the performance of the aircraft A (for instance airbrakes being implemented, minimization of the total distance DT followed on the ground, . . . ).

The means 12 thus determine a vertical profile PV linking the current energy state of the aircraft A to the energy state required at the stabilization point S (or at a point 24 linked to the runway 20 and described below). Furthermore, the means 12 determine said vertical profile PV according to one of a plurality of different building criteria, one of which is selected by default and the others could be selected by an operator (using means 3).

Preferably, the means 12 use, to this end, one of the following building criteria:

-   -   one first building criterion, wherein the stabilization point S         is directly linked to the current altitude, as shown on FIG. 3A;     -   one second building criterion, wherein a small level 25 at         constant altitude, just upstream of the stabilization point S,         as shown on FIG. 3B; and     -   one third building criterion, wherein a small level 26 at         constant altitude between the stabilization point S and the         current altitude, as shown on FIG. 3C.

The first part (length D on the ground) of the vertical profile PV (going up from the runway 20 to the aircraft A) remains on the approach axis 22 between the stabilization point S and the point 24 at 50 feet on the threshold of the runway 20. For this reason, the slope is fixed for this part.

Building the second part of the vertical profile PV could occur according to the above mentioned building criteria. Thus:

-   -   the simplest way involves directly reaching the height and the         current energy state of the aircraft A, so as to form the         vertical profile PV1 shown on FIG. 3A (length Dlim1 on the         ground for this second part);     -   a second solution therefore provides a small part 25 in level         (or at a reduced slope) before the stabilization point S so as         to avoid intercepting the final approach axis from the top, so         as to form the vertical profile PV2 shown on FIG. 3B (length         Dlim2 on the ground); and     -   a third solution, for forming the vertical profile PV3 shown on         FIG. 3C (length Dlim3 on the ground), takes into consideration         the case where the aircraft A intercepts the approach axis 22         before the stabilization point S. Preferably, the intersection         point of the level with the approach axis (in the vertical         plane) and the point where the trajectory of the aircraft A         reaches the approach axis (in the horizontal plane) when the         aircraft A meets it before the stabilization point S, are         matched. This supposes a calculation thru iterations for         determining the distance Dlim3 as a function of the energy to be         dissipated, since the distance between the end of the level 26         and the point S is not predetermined.

Furthermore, the means 13 determine a horizontal trajectory TH allowing the aircraft A to reach the stabilization point S, respecting the vertical profile PV determined by the means 12, that is allowing a dissipation of the energy from the aircraft A.

Furthermore, said means 13 determine this horizontal trajectory TH by implementing one of a plurality of different building rules, one of which is selected by default and the others could be selected by an operator (using means 3). Preferably, the means use, to this end, one of the following building rules:

-   -   one building rule, whereby an immediate turn is implemented, as         shown on FIGS. 4A and 5A;     -   one building rule, whereby the current heading (trajectory 27A,         27B) is held as long as possible, as shown on FIGS. 4B and 5B;         and     -   one building rule, whereby the current heading (trajectory 27A,         27B) is held up to the approach axis 22, as shown on FIGS. 4C         and 5C.

FIGS. 4A to 4C differ from FIGS. 5A to 5C, by a different relative position between the approach axis 22 and the current trajectory 27A, 27B followed by the aircraft A (according to the current heading), the current position of said aircraft A being represented by a symbol 28.

The means 13 determine afterwards the position of a first limit point on this trajectory TH, corresponding to the engagement at the latest of the approach phase on said trajectory. This position is illustrated:

-   -   by a symbol 29 shown in the shape of a lozenge in the example of         FIGS. 4A and 5A;     -   by a symbol 30 shown in the shape of a circle in the example of         FIGS. 4B and 5B; and     -   by a symbol 31 shown in the shape of a triangle in the example         of FIGS. 4C and 5C.

The previous FIGS. thus show three different ways to spread the distance Dlim on a trajectory linking the aircraft A to the selected target point S, as a function of the type of trajectory. The length of the thick continuous lines illustrating the trajectory TH (between S and the limit point) is always equal to Dlim (corresponding to the radius of the cercle C with a center S, being partially shown, in dashed lines, on these FIGS.).

Two additional display modalities could be mentioned:

-   -   the display of the circle C being particularly useful when the         distance between the aircraft and the stabilization point S is         higher than

Dlim (aircraft outside the circle: limit trajectory not calculated); and

-   -   a display of the limit heading instead of the limit trajectory.         The concept is easily applied to the cases shown on FIGS. 4A and         5A, and it could be extended with some variations to the cases         of FIGS. 4B and 5B. In this case, the limit trajectory is not         displayed, and, instead, a symbol is displayed representing the         heading beyond which the approach axis is likely to be         intercepted in excess of energy (the distance being followed is         too short), optionally accompanied by a particular symbol         corresponding to the interception point between the limit         trajectory calculated by the system and the approach axis.

In a preferred embodiment, said device 1 comprises a function being used when the aircraft A is located at a distance from the point S being lower than Dlim (thus inside the circle C centred on S and with a radius Dlim), as shown in the examples of FIGS. 6A to 6C.

In such a situation, for at least some types of trajectory, the means 14 determine, on the horizontal trajectory TH, the position of an auxiliary limit point corresponding to a point before which (that is upstream of which) it is not recommended to subject the aircraft to a turn.

A first case corresponds to the hypothesis of a type of trajectory, wherein the aircraft A rotates immediately toward the approach axis 22, as shown on FIG. 6A. The function shows the auxiliary limit point (shown by a square 33) where the approach axis 22 should be intercepted so as to avoid an over-energy situation. In the example of this FIG. 6A, it is not, for instance, possible to intercept the approach axis 22 more to the right with respect with the position of the point 33, if the energy of the aircraft A is to be dissipated.

A second case corresponds to the hypothesis of a type of trajectory wherein the aircraft A holds its current heading (trajectory 27A) as long as possible before turning toward the stabilization point S, as shown on FIG. 6B. The auxiliary limit point (represented by a square 34) corresponds to the turn point the earliest toward the approach axis 22, if the energy of the aircraft A is to be dissipated.

A third case corresponds to the hypothesis of a type of trajectory wherein the aircraft A holds its current heading (trajectory 27A) as long as possible, until intercepting the approach axis 22, as shown on FIG. 6C. In such a case, it is not necessary to define an auxiliary limit point. Should it be defined, it would correspond to the intersection of the current path (trajectory 27A) of the aircraft A with the approach axis 22. 

1. A method for aiding the approach of an aircraft (A), in particular of a transport airplane, upon an approach phase for the purpose of landing on a landing runway (20), wherein, automatically and repeatedly: A/ a limit trajectory (TL) is built representing a flight trajectory of the aircraft (A) being compatible with the performance of said aircraft (A) upon the approach and which shows the limits in which the aircraft (A) can move around, implementing the following operations consisting in: a) receiving the current speed vector of the aircraft (A) and position data, relative to the landing runway (20) and to a stabilization point(s); b) determining as a function of the performance of the aircraft and of its current speed vector, a vertical profile (PV1, PV2, PV3) which shows the variation of the height and of the speed of the aircraft (A) as a function of a distance and being such that it allows to dissipate the energy of the aircraft (A) upon the approach, the energy state at said stabilization point (S) corresponding to a required energy state; c) determining a horizontal trajectory (TH), allowing the aircraft to reach the stabilization point (S), respecting the vertical profile (PV1, PV2, PV3) determined at step b); and d) determining the position of a limit point (29, 30, 31) on this horizontal trajectory (TH), corresponding to the engagement at the latest of the approach phase according to the limit trajectory; and B/ the limit trajectory (TL) is automatically shown comprising said horizontal trajectory (TH) and said limit point (29, 30, 31), on a viewing screen (9) in the cockpit of the aircraft.
 2. The method according to claim 1, characterized in that at step A/b), a vertical profile (PV1, PV2, PV3) is determined linking the current energy state of the aircraft (A) to the energy state required at the stabilization point (S).
 3. The method according to claim 1, characterized in that at step A/b), said vertical profile (PV1, PV2, PV3) is determined according to one of a plurality of different building criteria, one of which is selected by default and the others could be selected by an operator.
 4. The method according to claim 3, characterized in that one of the following building criteria is used for determining the vertical profile (PV1, PV2, PV3): one building criterion, wherein the stabilization point (S) is directly linked to the current altitude; one building criterion, wherein a constant altitude level (25) is provided at the stabilization point (S); and one building criterion, wherein a constant altitude level (26) is provided between the stabilization point (S) and the current point.
 5. The method according to claim 1, characterized in that at step A/, a prediction of the current speed vector of the aircraft (A) is carried out.
 6. The method according to claim 1, characterized in that at step A/c), the horizontal trajectory (TH) is determined according to one of a plurality of different building rules, one of which is selected by default and the others could be selected by an operator.
 7. The method according to claim 6, characterized in that one of the following building rules is used for determining the horizontal trajectory (TH): one building rule, whereby an immediate turn is carried out; one building rule, whereby the current heading is held as long as possible; and one building rule, whereby the current heading is held until the approach axis (22).
 8. The method according to claim 1, characterized in that at step A/, on the horizontal trajectory (TH), the position of an auxiliary limit point (33, 34) is determined corresponding to a point before which it is not recommended to subject the aircraft (A) to a turn.
 9. A device for aiding the approach phase of an aircraft (A), in particular of a transport airplane, upon an approach phase for the purpose of landing on a landing runway (20), said device (1) comprising: a processing unit (4) for automatically building a limit trajectory (TL) representing a flight trajectory of the aircraft (A) being compatible with the performance of said aircraft (A) upon the approach and which shows the limits in which the aircraft (A) can move around, said processing unit (4) comprising: means (11) for receiving the current speed vector of the aircraft (A) and position data, relative to the landing runway and to a stabilization point (S) means (12) for determining, as a function of the performance of the aircraft (A) and of its current speed vector, a vertical profile (PV1, PV2, PV3) which shows the variation of the height and of the speed of the aircraft (A) as a function of a distance and being such that it allows to dissipate the energy of the aircraft (A) upon the approach, the energy state at said stabilization point (S) corresponding to a required energy state; means (13) for determining a horizontal trajectory (TH) allowing the aircraft to reach the stabilization point (S), respecting said vertical profile (PV1, PV2, PV3); and means (14) for determining the position of a limit point (29, 30, 31) on this horizontal trajectory (TH), corresponding to the engagement at the latest of the approach phase according to the limit trajectory; and displaying means (7) for automatically presenting the limit trajectory (TL) comprising said horizontal trajectory (TH) and said limit point (29, 30, 31), on a viewing screen (9) in the cockpit of the aircraft.
 10. The device according to claim 9, characterized in that it further comprises means (15) for manually activating the display of the limit trajectory (TL) on said viewing screen (9).
 11. The device according to claim 9, characterized in that it further comprises means (17) for automatically activating the display of the limit trajectory (TL) on said viewing screen (9).
 12. The device according to claim 9, characterized in that it further comprises means (14) for determining, on the horizontal trajectory (TH), the position of an auxiliary limit point (33, 34) corresponding to a point before which it is not recommended to subject the aircraft (A) to a turn.
 13. An aircraft, characterized in that it comprises a device (1) such as specified in claim
 9. 